The Changing Face of Infection-Related Glomerulonephritis: Klebsiella's Hidden Threat

Introduction: Infection-related glomerulonephritis (IRGN) has become more recognized as a cause of kidney disease, particularly in the elderly and immunocompromised, often with active infections at diagnosis. While most cases are linked to streptococcal and staphylococcal species, gram-negative bacteria have also been identified as culprits. This case highlights Klebsiella as a cause of IRGN. Case Description: An 81-year-old male with a history of HTN and CVA, presented with left flank pain, lower limb edema and oliguria. No recent URTI, cellulitis or PNA. Pertinent labs showed Cr 9 from a normal baseline, BUN 78, UA with RBCs and protein. Complements and ANCA were unremarkable. Abdominal imaging showed a large 8cm left renal abscess. He was started on Ceftriaxone; blood cultures remained negative. Abscess was drained, and cultures grew pan-sensitive Klebsiella pneumoniae. ECHO was negative for vegetation. Kidney biopsy showed Immune complex-mediated proliferative glomerulonephritis with fibrocellular crescents and dominant C3 and IgA containing immune complex deposits, EM showed immune complex deposits in the mesangium and in the capillary loops. Suggestive of IRGN. Discussion: IRGN is historically linked to streptococcus and staphylococcus, especially MRSA; where superantigens like staph enterotoxins trigger massive T-cell activation and proinflammatory cytokine release. Gram-negative bacteria cause 10% of IRGN cases. Klebsiella has diverse genetics with multidrug resistance and virulence factors like capsule polysaccharides and lipopolysaccharides. J.W. Forrest Jr. et al. found in kidney biopsies from Klebsiella cases that capsular polysaccharide antigens were deposited with immunoglobulins and complement components in the glomeruli. These antibodies were strain-specific, suggesting that these antigens are highly immunogenic and may trigger inflammation and cytokine release similar to staph superantigens.